Unlocking the Huawei E5830 aka 3 Mifi. 3 will post you an unlocked replacement for your MiFi for £15, if you can figure out how to ask them to do it. Reports on the internet are that it can take several weeks and they sometimes forget to unlock the one you send them, so I went the self-unlocking route. These instructions (involving Windows running in VMWare Fusion, Firmware updates, PayPal, some very dodgy looking software and a PDF file half-written in Japan) ended up working a treat.